I have learned this through decades of research and development on identity and leadership. Leaders with strong identities stay steady while others falter. They can handle the eventual necessary transfer of power, because who they are is not dependent on external factors or outside opinions. They validate themselves.
Allowing others to shine a light on our blind spots, particularly with respect to our faults, teaches us how to become better conversationalists, better listeners, and ultimately, better people in general. What we learn about our blind spots may not always be pleasant, but it can open up a whole new world we never even knew existed.
Our war in Iraq was fundamentally a war of choice, and it was the wrong choice -- a war fought on false pretenses and for false purposes. But this "cake-walk" became an occupation, with years of vicious and deadly street warfare, sectarian violence, constant terrorist bombings, and finally no real political solutions to unite the country.